Self-tightening coupler

ABSTRACT

A radially expandable body having a cylindrical bore and longitudinally slotted to provide access thereto is coupled to a smooth shaft within said bore by tangential insertion of a thin flexible filler strip. The body may fit within a hub for coupling said hub to said shaft.

United States Patent 1 Nestor Feb. 5, 1974 [5 SELF-TIGHTENING COUPLER3,203,716 8/1965 Lannenn 29/526 [75] Inventor: Leonard R. Nestor St.Paul Minn. 2,756,484 7/1956 Booth 29/526 M M' d [73] Asslgnee zlz iz z ggi zg St Paul Primary Examiner.lordan Franklin Minn AssistantExaminerConrad L. Berman Attorney, Agent, or Firm-Alexander, Sell,Steldt and [22] Filed: Oct. 5, 1972 DeLal-lunt [2!] Appl. No.2 295,161

52 us. a 403/351, 403/365, 403/367 [57] BSHMCT [5]] Int. Cl. Fl6d 1/06 Aradially expandable body having a cylindrical bore [58] d of Search287/5209 5204 and longitudinally slotted to provide access thereto is287/1 115; 285/305; 29/526 433; coupled to a smooth shaft within saidbore by tangen- 403/243, 350, 351, 352, 365, 367 tial insertion of athin flexible filler strip. The body [56] References Cited isililzgyttfit within a hub for coupling said hub to said UNITED STATES PATENTS6/1928 Brent 287/5209 15 Claims, 7 Drawing Figures 1 SELF-TIGHTENINGCOUPLER This invention relates to the mounting of machine parts onrotating shafts. The invention provides an inexpensive and uncomplicatedself-tightening coupler device which, while not limited thereto, hasbeen found to be particularly useful in coupling small plastic rotaryfans to smooth metal drive shafts.

Attempts to use prior art coupling devices, such for example as keys andset screws, on plastic hubs frequently results in cracking or chippingof the hub due to the inherent lack of strength in the plastic material.Insertion of metal cores or bushings, e.g. during molding of the plasticpart, provides increased strength to resist the disruptive effects ofkeys and set-screws but is time-consuming and expensive.

The present invention provides a self-tightening coupler of simplifiedconstruction. The coupler is easily inserted between shaft and hub andis then tightened against both surfaces merely by rotation of the two. Atigh slip-resistant fit is obtained but without such excessive orlocalized stresses as might cause failure of the hub and withoutrequiring previous roughening or deformation of the shaft. Both plasticand metal constructions are effective. The same principle is applicableto cams, stops, and other generally tubular structures required to berigidly mounted on smooth shafts.

In the drawing,

FIG. 1 is an end elevation showing a coupler supporting a plastic fanhub on a metal shaft,

FIG. 2 is a side elevation of the coupler of FIG. 1,

FIG. 3 is an end elevation of a self-contained coupler,

FIG. 4 is a view in perspective, of another form of self-containedcoupler, 1

FIG. 5 is a side elevation of a tapered coupler body,

FIG. 6 is an end elevation of a multi-faceted coupler body, and

FIG. 7 is an end elevation ofa coupler having a multigrooved body.

The coupler 10 of FIGS. 1 and 2 comprises a generally tubular body 11slotted longitudinally and tangentially of the central bore to providean entry slot 12 and grooved longitudinally along the outer portiongenerally opposite the inner mouth of the slot 12 to form a shallowgroove 13 and leave a relatively thin section 14 of increasedflexibility. A thin flexible liner strip 15 extends from the slot 12into the annular space 16 between the body ll and a shaft 17 where it istightly held. A hub 18 here'shown as the hub of a fan with the bladesbroken away for convenience is illustration, fits around the couplerassembly.

The parts are assembled as follows. The body 11 is first slipped ontothe shaft 17 and the strip 15 is fed through the slot 12 and into theannular opening 16. Relative rotation of body and shaft then draws thestrip into the annular space and is continued until sufficient of thestrip has been taken up to cause a preliminary tightening. Any extendedor excess strip is removed and the assembly is placed within the hub 18.Further rotation of the body on the shaft then draws the remainingsegment of the strip into the annular space, causes radial expansion ofthe body against the interior surface of the hub, and tightens the bodyonto the shaft. Radial expansion of the body is facilitated by the hingeeffect obtained at the thin section 14. As the coupler expands andbegins to grip the hub, torque is readily applied through the hub itselfso that a tight fit is quickly and easily attained.

In the device of FIGS. 1 and 2 the removal of excess strip, prior toapplying the hub, leaves only a short segment within the slot 12 forcompleting the compression fit, and it is therefore necessary to obtaina relatively tight preliminary fit before removing the excess. Thestructures shown in FIG. 3 and in FIG. 4 illustrate two improvedstrip-supplying means. The size of the slot 32 in body 31 of FIG. 3 isexpanded within the wall of the body to form a cylindrical opening 39within which a major portion 'of the strip 35 is coiled. Additionallength of strip is thus provided, to be drawn into the annular space forfurther expanding and tightening the coupler. In the coupler 40 of FIG.4 an outer annular channel 49 provides sufficient space for aconsiderable length of liner strip 45, the outer ridges 41 then makingcontact with the inner surface of the hub when the strip 45 is forcedthrough the open-mouthed slot 42 and around a shaft.

Where desired, the tubular body may have an other than cylindricalperiphery. The body 51 of FIG. 5 is tapered to fit within acorresponding tapered hub. The body 61 of FIG. 6 has a hexagonal shapeproviding at each facet a thinner section 64 between the periphery andthe bore for permitting radial expansion. The grooves 73 and lands 74 ofthe body 71 of FIG. 7 similarly provide sections of increasedflexibility for permitting expansion of the body on forced entry of astrip 75 through the slot 72 and around a shaft. Where a hub isincluded, it may be, and preferably is, provided with cooperating facetsor splines, as illustrated in FIG. 6 by internally faceted hub 68.

Placing the entry slot tangent to the inner bore of the body providesfor maximum ease of insertion of the liner strip and is generallypreferred, particularly where shaft and body are relativelyclose-fitting. With more loosely fitting pieces, or where theinner'edges of the slot are appropriately rounded or chamfered, the slotmay lie along a radial plane or at some intermediate angle. The slot 42of FIG. 4 will be seen to be defined by one tangential and one radialface providing for exceptionally easy insertion of thestrip 45 but alsoproducing an unduly wide break in the outer periphery.

Thin flexible metal shim stock may be used as the liner strip, in whichcase the inner end of the strip may if necessary be adhered to, orotherwise prevented from sliding on, the surface of the shaft, forexample using a small amount of self-tacky adhesive, in starting thestrip into the annular space between shaft and body. A preferredstructure employs an abrasivecoated strip, such for example as a stripof thin, tough, high tensile strength polyethylene terephthalatepolyester foil having bonded to one surface a layer of very fineabrasive grit. A product known as lapping film, typically havingnominally 30 micron silicon carbide grit bonded to 3 mil (0.075 mm.)polyester film to a total thickness of 5 mils (0.125 mm.), has beenfound eminently satisfactory. The abrasive surface faces andfrictionally grips the surface of the shaft, while the uncoated surfaceof the strip slides easily against the inner surface of the body tofacilitate application of the coupler.

The liner strip may be the full width of the body, or some lesser width.In the structure shown in FIG. 4 the width of the strip will be nogreater than the width of the channel 49 between the ridges 41. Two ormore simple reinforcing ring may be placed over the coupler body toprovide further tightening capability or to avoid possible breakage ofthe body member.

Expansion slots, such as the slot 13 in the device of FIG. 1, areessential where the body 1 1 is otherwise unduly rigid or is susceptibleof breakage, but may be dispensed with when using sufficiently thin andtough body structures, as indicated by the following specificillustrative examples. In one, a body 11 of polystyrene, having an axiallength of 15 mm., outside diameter of 22 mm., and inside diameter of 12mm., is desirably provided with a slot 13 having a depth of 2.5 mm. andsituated at a position approximately opposite the inner opening of thetangential slot-l2 as shown in FIGS. 1 and 3, in order to permit fullyadequate radial expansion without cracking of the body. By way ofcontrast, in another example a body member, constructed of aluminumalloy to a length of 25 mm., with an outside diameter of 26 mm., insidediameter of 18.5 mm., and circumferentially channeled to a depth of 1mm., requires no expansion slot. Both bodies are used with a fillerstrip of lapping film. The polymeric body is best used as shown in FIG.1, i.e. within a surrounding hub or other reinforcing ring. The metalbody may be similarly used, but in addition may be applied in theabsence of any outer reinforcement, for example as a stop or cam.Application of either form of coupler to a smooth metal shaft underhand-applied torque produces such a tight fit as to require the use of awrench for subsequent removal.

What is claimed is as follows:

1. A self-tightening coupler for fitting onto a smooth surfacedcylindrical shaft, comprising a radially expandable body member having acyindrical shaftreceiving bore and slotted along its entire length toprovide a narrow access slot from the periphery to said bore, and a thinfiller strip inserted through said slot for advancing between the outerperiphery of said shaft and the body surface defining said bore uponrelative rotation of shaft and body to provide a tight frictional fitbetween shaft, strip and body.

2. Coupler of claim 1 wherein said body member is generally tubular withat least one longitudinal section of reduced wall thickness forfacilitating radial expansion. 7

3. Coupler of claim 2 wherein said body member is longitudinally groovedopposite the access slot.

4. Coupler of claim 2 wherein said slot is enlarged within the wall ofsaid body to provide a cavity, and

wherein at least a portion of said strip is stored within said cavity.

5. Coupler of claim 2 wherein said body is exteriorly channeled toprovide an annular channel, and wherein at least a portion of said stripis stored within said channel.

6. Coupler of claim 1 including a reinforcing ring circumferentiallysurrounding said body.

7. Coupler of claim 1 wherein said filler strip includes means forproviding higher frictional forces between itself and a shaft insertedwithin said bore than between itself and the body surface defining saidbore.

8. Coupler of claim 7 wherein said strip has bonded to one surface alayer of abrasive particles.

9. A structure comprising a radially expandable body member having acylindrical bore and an access slot along its entire length extendingfrom the periphery to the bore, a smooth-surfaced cylindrical shaftpassing through said bore, and a thin flexible filler strip insertedradially through said slot and compressed between said shaft and theinner surface of said body member to an extent sufficient to causeradial expansion of said member and tight frictional engagement betweenbody member and shaft.

10. Structure of claim 9 wherein said body member is generally tubularwith at least one longitudinal section of reduced wall thicknessfacilitating said radial expansion.

11. Structure of claim 10 wherein said body member is longitudinallygrooved opposite the access slot.

12. Structure of claim 1 1 including a reinforcing ringcircumferentially surrounding said body and wherein said body isradially expanded into tight-fitting contact with said ring.

13. Structure of claim 12 wherein said ring is a hub for a rotativedevice.

14. Structure of claim 9 wherein said body member is externallychanneled to provide an annular channel of a width at least that of saidfiller strip.

15. Structure of claim 10 wherein said body member has a faceted orgrooved exterior surface and is in tightfitting contact with the innercooperatively faceted or splined surface of a reinforcing ring.

* :r a: a:

1. A self-tightening coupler for fitting onto a smooth surfacedcylindrical shaft, comprising a radially expandable body member having acyindrical shaft-receiving bore and slotted along its entire length toprovide a narrow access slot from the periphery to said bore, and a thinfiller strip inserted through said slot for advancing between the outerperiphery of said shaft and the body surface defining said bore uponrelative rotation of shaft and body to provide a tight frictional fitbetween shaft, strip and body.
 2. Coupler of claim 1 wherein said bodymember is generally tubular with at least one longitudinal section ofreduced wall thickness for facilitating radial expansion.
 3. Coupler ofclaim 2 wherein said body member is longitudinally grooved opposite theaccess slot.
 4. Coupler of claim 2 wherein said slot is enlarged withinthe wall of said body to provide a cavity, and wherein at least aportion of said strip is stored within said cavity.
 5. Coupler of claim2 wherein said body is exteriorly channeled to provide an annularchannel, and wherein at least a portion of said strip is stored withinsaid channel.
 6. Coupler of claim 1 including a reinforcing ringcircumferentially surrounding said body.
 7. Coupler of claim 1 whereinsaid filler strip includes means for providing higher frictional forcesbetween itself and a shaft inserted within said bore than between itselfand the body surface defining said bore.
 8. Coupler of claim 7 whereinsaid strip has bonded to one surface a layer of abrasive particles.
 9. Astructure comprising a radially expandable body member having acylindrical bore and an access slot along its entire length extendingfrom the periphery to the bore, a smooth-surfaced cylindrical shaftpassing through said bore, and a thin flexible filler strip insertedradially through said slot and compressed between said shaft and theinner surface of said body member to an extent sufficient to causeradial expansion of said member and tight frictional engagement betweenbody member and shaft.
 10. Structure of claim 9 wherein said body memberis generally tubular with at least one longitudinal section of reducedwall thickness facilitating said radial expansion.
 11. Structure ofclaim 10 wherein said body member is longitudinally grooved opposite theaccess sloT.
 12. Structure of claim 11 including a reinforcing ringcircumferentially surrounding said body and wherein said body isradially expanded into tight-fitting contact with said ring. 13.Structure of claim 12 wherein said ring is a hub for a rotative device.14. Structure of claim 9 wherein said body member is externallychanneled to provide an annular channel of a width at least that of saidfiller strip.
 15. Structure of claim 10 wherein said body member has afaceted or grooved exterior surface and is in tight-fitting contact withthe inner cooperatively faceted or splined surface of a reinforcingring.